1. Field of the Invention
The present invention is in the field of rear projection display systems and, more specifically, three-dimensional rear projection screens that are formed as a human face and projected onto a translucent convex surface to provide an illusion of an actual human face when viewed from a concave surface of the screen.
2. Description of Related Art
In recent years much attention has been given to transforming two-dimensional television and computer displays into more realistic three-dimensional displays. Although great strides have been made with certain types of three-dimensional displays, this type of display generally still lacks properties needed to actively engage an observer in a natural and personal way. Any three-dimensional illusion is rapidly destroyed as the observer moves about relative to the display because an image of the person imaged on the display, whether from a live or recorded source, fails to match the movements of the observer. For example, a newscaster should look straight ahead into the camera and thereby looks straight ahead towards the observer positioned directly before the display. This produces a sense of personal interaction because the newscaster appears to look directly at the observer. However, when the observer changes position, this sense of personal interaction is spoiled because the imaged newscaster fails to turn toward the observer in a natural manner. This lack of natural movement also retards natural conversation during video-conferencing because an image of a conferee does not follow a party conversing with the image.
The illusion of an actively moving head was probably originally observed in the negative impression of a person's face in a plaster mold. When one looks into a concave side of a mold of a human face, one observes a positive face, that is, an apparently concave image, which appears to turn as the observer moves from side to side before the concave mold. The illusion lacks nothing more than color and live action to create a unique sense of interpersonal engagement.
In the past a film projector in a front projection configuration has been used with some success to provide an illusion of full motion to a concave face screen. That is, a film of an actor's face can be projected onto a properly-shaped concave screen to provide a realistic illusion of a living face. These front-projected face screens have been used at several theme parks as parts of rides. The drawbacks of this front projection configuration are numerous. The viewing environment must be kept dark so that the projected image is not washed out by ambient light. Observers must be kept at a significant distance so as to not interfere with the projection beam. Also, distance helps reduce awareness of looking into the concave or negative side of the mold, thereby fostering the illusion that the observer is viewing a moving convex face.
A major drawback with this illusion is that accurate eye contact between the concave face image and the observer is not achieved. The head-shaped screen and especially the eyes, although configured to accurate human facial dimensions, appear to move more quickly than the observer's movements. The result is a lack of personal engagement because the imaged person is looking away rather than directly at the observer as that observer moves relative to the screen. This is no doubt a product of the optical illusion that produces an illusion of a concave rather than a convex image, and will be discussed below. Another drawback is that at the sides of the field of view the face image takes on a distorted and unnatural appearance which reveals the concave nature of the screen, thereby shattering the optical illusion.
In an attempt to resolve some of the drawbacks of the front projection face screen one of the instant inventors, Machtig, developed a rear projection face screen. A film projector and, later, an LCD (liquid crystal device) television projector, was used to project an image of a person onto the convex side of a diffused translucent face screen. When viewed from the concave side, an optical illusion of a living concave head was produced. This approach proved superior to the front projection method because observers could walk in front of the screen and not disturb the projected image. However, as with the front projection system, the illusion of accurate movement matched to that of the observer was not achieved with a screen configured to the natural dimensions of the human face. This lack of accurate movement also prevented eye contact. When the observer moved to the side, the image appeared to shift its gaze, but ended up looking away rather than directly at the observer. The illusion also suffered from deterioration when observed from the sides of the field of view, that is, beyond a viewing angle of about 15 degrees from the center. The imaged person appeared to be unnaturally distorted with part of the face cut off. Finally, while the rear projection technique permitted observers to view the concave face screen in close proximity because there was no disturbance to the projector beam, such close viewing allowed the observers to realize the concave shape of the screen, thereby destroying the illusion.